Stepwise operating driving device



Aug. 25, 1959 c; GREVE 2,900,840

STEPWISE OPERATING DRIVING DEVICE Filed Dec. 10, 1957 0 INVENTOR REINHARD CORNELIS GREVE BY M AG |T STEPWISE OPERATING DRIVING DEVICE Reinhard Cornelia Grev e, Hilversum, Netherlands, as-

signor to North American Philips Company, Inc., New York, N.Y., a corporation of Delaware Application December 10, 1957, Serial No. 701,798

Claims priority, application Netherlands December 22, 1956 3 Claims. (Cl. 74-575) 'driven selectors for use in automatic telephone systems.

With a known drivingdevice of this kind the pawl end co-operating with the pawl wheel and the guide surface is shaped in the form of a uniformly thick, flat pin. In this case the pawl is secured to a blade spring connected to the armature of an electro-magnet. The blade spring permits the pin-shaped end of the pawl, when returning, of moving precisely in its direction of length.

The invention has for'its object to provide a driving device comprising a pawl of a simple shape, which is adapted to be connected directly with its driving memher.

In accordance with the invention the two pawl edges co-operating with the teeth of the pawl wheel and the guide surface of the stop respectively are circular and the common centre of the edges lies in between them.

The structure according to the invention has the advantage that during the return movement of the pawl rotation of the pawl is permitted, so that the pawl may be connected directly to the armature of a magnet or a further driving member which performs a rotary movement.

The two said edges of the pawl may be caused to follow the same circle; it is often more advantageous to have a radius of the edge co-operating with the teeth of the pawl wheel which is smaller than that of the edge cooperating with the guide surface.

The invention will be described-with reference to the drawing, which shows one embodiment. In the drawmg- Fig. 1 shows diagrammatically a driving device according .to the invention, viewed in a direction transverse to the pawl wheel,

Fig. 2 shows, on an enlarged scale, part of the pawl wheel and the pawl end cooperating herewith in the device shown in Fig. 1.

Referring to Fig. 1, reference numeral 1 designates the yoke of an electro-magnet 2, which is provided with an excitation coil 3. An armature 4 is secured rotatably at the area 5 to one limb of the yoke l and is held spaced United States Patent apart from the other limb of the yoke, in the deenergized I state of the magnet 2, by a spring 6 secured to a fixed point 7. The free end of the armature 4 is provided with a pawl 8, which is rotatably secured thereto. The end 9 of this pawl co-operates with the teeth 10 of a pawl wheel 12, seated on a rotary shaft 11, and with the guide surface 13 of a stationary stop 14. The pawl end 9 has two circular edges 15 and 16, which cooperate with the teeth 10 and the guide surface 13 respectively, said surface Patented Aug. 25, 1959 being substantially parallel to the tooth surface 17, in contact with the pawl end 9, during the return stroke of said pawl. The circular edges 15 and 16 have a common centre 20 lying in between them.

With the teeth of the pawl wheel 12 co-operates, in addition, a pivotable return pawl 18, which is urged towards the teeth 10 by means of a blade spring 19.

The device described operates as follows. In the position shown the magnet 2 is not energized. The armature 4 and the pawl 8 occupy the extreme right-hand position owing to the spring 6. When the electro-magnet 2 is energized, the armature 4 is attracted by the yoke 1 against the force of the spring 6, the end 9 of the pawl 8 being thus moved to the left. The return pawl 19 prevents the pawl wheel 12 from being rotated against the direction of rotation indicated by the arrow P. The circular shape of the edges 15 and 16 of the end 9 of the-pawl provides that the relative distance between the less steep tooth edge 17 and the guide surface 13 cannot be reduced, in spite of a slight rotation of the pawl 8 due to the rotation of the armature about the point 5. This means, consequently, that the pawl wheel 12 cannot move in the direction P during the motion of the pawl 9 to the left. The arrangement of the electro-magnet 2 is such that at the end of the stroke of the armature 4 the pawl with the edge 15 falls behind that tooth 10, of which the edge 17 forms part.

As soon as the pawl end 9 passes by the said tooth, the pawl 8 falls into the next-following interstice between the teeth under the action of a blade spring 21, secured to the armature 4. When the energization of the electromagnet 2 is interrupted, the armature 4 with the pawl 8 are moved again to the right by the spring 6, the pawl wheel 12 being thus rotated in the direction P over a tooth interspace until the next-following rest position is reached. The circular shape of the edges of the end 9 of the pawl 8 permits the pawl of being displaced not only linearly but also rotatably. This permits a direct connection of the pawl with the armature and permits of choosing a comparatively small distance between the pivot point of the armature and the pivot point of the pawl.

The two circular edges 15 and 16 may form part of the same circle, the centre of which lies in the centre between the edge 17 and the guide surface 13. With the embodiment described the radius of the edge 15 is, however, smaller than that of the edge 16. This has the advantage that the pawl end 9, when the pawl 8 rotates, is less likely to be jammed against the steep edge of a tooth 10 at the beginning of the return motion.

The pawl 8 is preferably made of linear superpolyamide (nylon). This has the advantage both of a small wear and a low amount of noise during the operation of the device.

What is claimed is:

l. A stepwise driving device comprising a toothed pawl movement wherein said pawl co-acts with the teeth of said pawl wheel, a stationary stop member having a guide surface, said guide surface and said toothed edge being substantially parallel during the return stroke of said pawl, said pawl having two edges, said two edges of said pawl co-operating with the teeth of the pawl wheel and the guide surface of the stop respectively, and said edges are curvilinear and the common center of said edges lies therebetween.

2. A stepwise driving device comprising a toothed pawl wheel, a pawl, means mounting said pawl for rocking movement wherein said pawl co-acts with the teeth of said pawl wheel, a stationary stop member having a guide surface, said guide surface and said toothed edge being substantially parallel during the return stroke of said pawl, said pawl having two edges, said two edges of said pawl co-operating with the teeth of the pawl wheel and the guide surface of the stop respectively, said edges are curvilinear and the common center of said edges lies therebetween, and the radius of the edge co-aeting with the pawl wheel is smaller than'the radius of the edge coacting with said guide surface.

3. A stepwise driving device as claimed in claim 1 wherein said pawl is constituted of a linear supeipolyamide.

References Cited in the file of this patent 

